What are all the forces a person is subjected to in a G force simulator?


In a G force centrifuge a test pilot is exposed to high G forces, however recently I've been learning about centripetal force and the coriolis force (pseudo force). I became a little confused when considering a G force centrifuge as prior to considering these forces properly I presumed the only force acting on the test pilot was the centripetal force, thats why in videos of them you see a little G force counter telling you how many g's the pilot was dealing with before he/she passed out.

The images show a representation of a pilot inside a G force centrifuge. The pilot is denoted by the bronze/gold geometry, the circular end representing the pilots head and the square end representing the pilots feet, the platform the pilot is attached to represents his feet.

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Now as I understand it, when the centrifuges rpm increases the pilots blood begins to pool towards his feet which is the centripetal force, I understand that and know how to approximately calculate it

F = Mass (Velocity^2) / radius

However there is also the force of earths gravity which doesn't increase or decrease as the centrifuge spins, but my main question is, isn't there another force accelerating the pilot into his seat and that force is dependant on the rpm, even when the rpm has levelled out and is constant, that force is still there pinning our pilot into his seat. Is that the case? Or as long as the pilot survives the acceleration he is no longer pinned to his seat and the only force he now feels is the centripetal force?

Is the force pinning the pilot to his seat the coreolis effect and if so is the velocity component of the coreolis equation the speed at which the pilot is traveling along the circumference of the circular path?


1 Answer 1


The way you describe the forces depends on the reference frame you choose. You can choose the lab frame, in which the pilot is whizzing around in circles---then there's only centripetal force (ignoring gravity) but the pilot is experiencing a large acceleration. But it's more convenient to choose the pilot frame--you're interested in the experience of the pilot, so it makes sense to consider it from her point of view.

In this frame, the pilot is stationary, and besides the centripetal force on her feet (or her butt, if she's sitting), there's a centrifugal force. This is a pseudo-force--it only exists because the frame is not inertial--but to the pilot it's very real. It creates an effect just like gravity (but pointing outward), making her feel much heavier than normal.

There is in general a second pseudo-force in rotating frames: the Coriolis force. That is zero here because the pilot is not moving in her own frame. If she started to wave her arms around, she'd feel the Coriolis force pushing on them.

  • $\begingroup$ 'There is in general a second pseudo-force in rotating frames: the Coriolis force. That is zero here because the pilot is not moving in her own frame. If she started to wave her arms around, she'd feel the Coriolis force pushing on them.' That confuses me a bit, so the pilot doesn't feel pressed against her seat? It makes sense when you look at the equation but I'm struggling with that intituively, if she tried to stand up and take a step forward ( presuming there was room for that) she would only then feel the coriolis force? $\endgroup$ Commented Feb 17, 2021 at 18:17
  • $\begingroup$ She absolutely feels pushed against her seat. That is the centrifugal force, one the two pseudo forces, the other of which is the Coriolis force. The centrifugal force does not depend on her velocity, Coriolis does. $\endgroup$
    – Ben51
    Commented Feb 17, 2021 at 18:19
  • $\begingroup$ I understand the centrifugal force, blood is being driven to her feet and she is being pushed agaisnt her seat, if there was an arrow it would be pointing from her head down, but what i was refering, is she being pressed against her seat, in my mind there would be a second force pushing her to the back of her seat, the arrow of force pointing from her chest to her back. That's what I can't grasp. $\endgroup$ Commented Feb 17, 2021 at 18:22
  • $\begingroup$ If the rotation rate is constant, there is no force pushing her into the back of her seat. If the rotation rate is speeding up, there is a third pseudo force, called the Euler force, pushing her backward. $\endgroup$
    – Ben51
    Commented Feb 17, 2021 at 18:24
  • $\begingroup$ Ah, so if you stay still and have overcome the Euler force by for lack of a better word adapting to the speed, you could hypothethically spit out some water in front of your face and it wouldn't fly back into your face, it would just go to the ground like it would in a moving car? $\endgroup$ Commented Feb 17, 2021 at 18:28

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